In battery operated systems such as remote measurement or control devices, battery life is a critical success factor. In order to maximize battery life, the components which make up these systems are designed to minimize the power consumed to perform a function (active power) and also minimize the power when the component is in an in-active state (standby power). VLSI components in these systems are expected to be designed and operated in such a way as to minimize the active and standby power.
Most VLSI devices are designed to operate at a pre-defined minimum voltage. These devices are then operated within a voltage specification whose low end is the pre-defined minimum voltage with a predetermined margin. This is done to guarantee the correct operation of all the circuits in the VLSI device. Any VLSI device may have a plurality of voltages, and each of these voltage domains has a voltage range of operation.
There is a variation in the process of manufacturing the VLSI device where the characteristics of the device vary within a range, known as the process variance. The device is often designed to the most stringent of these ranges, and for the lowest voltage of the voltage range. This causes the devices that are not at the most stringent end of the process variance to be highly over-designed, even at the lowest rated voltage range of the process. Since the device was not designed for a voltage range below the lowest rated voltage, the manufacturer of the VLSI device does not guarantee the operation of this device below the lowest voltage in the range, even though the device may be capable of operating at a much lower voltage.